Recently, an antenna installed in a mobile communication device is manufactured while focusing on a small size and multi-functions. Although the size of a portable terminal has become small-sized, the portable terminal is requested to support various services such as reproduction of video and audio files or application execution. Thus, the antenna for the portable terminal is also requested to have various functions with a small size.
A sub-antenna installed in a portable mobile terminal includes a metal plate antenna having a PIFA (Planar Inverted-F Antenna) structure and a ceramic chip type antenna. Although the performance of the metal plate antenna is lower than that of an external antenna, the metal plate antenna has a merit in that the metal plate antenna can be built in the mobile terminal. However, it is difficult to ensure an installation space for the metal plate antenna due to the large size of the metal plate antenna. Since the design of the metal plate antenna must be changed according to the type of portable devices, there is a problem of increasing the manufacturing cost of the metal plate antenna.
Meanwhile, although the ceramic chip type antenna is small in size, the antenna tuning of the ceramic chip type antenna is difficult. In addition, the ceramic chip type antenna is sensitive to external factors due to its narrow bandwidth. Further, the performance of the ceramic chip type antenna is degraded, so it is difficult to fabricate an antenna, which is easily embedded, has a large bandwidth and an excellent performance.